Atalopharetra, Mesibov, Robert, 2005

Mesibov, Robert, 2005, (Diplopoda: Polydesmida: Dalodesmidae) from Tasmania, Australia, Zootaxa 1034, pp. 21-42 : 22-23

Atalopharetra n. gen.

Type species: Atalopharetra johnsi n. sp., by present designation.

Other assigned species: A. bashfordi n. sp., A. clarkei n. sp., A. eberhardi n. sp.

Diagnosis: Medium­sized dalodesmids (males 18–22 mm long) with pore formula 5, 7, 9, 10, 12, 13, 15–19; telopodite with large, curved, laminar process or processes distally forming a “hood” partly containing solenomere. Distinguished from similarly hooded Bromodesmus Mesibov, 2004 by short and broad rather than long and slender telopodite, and by stout and blunt rather than long and needle­like solenomere.

Etymology: Greek atalos (“delicate”) + pharetra (“quiver for arrows”), feminine, referring to the containment of the solenomere within the hood­like process(es) of the gonopod telopodite. This name was suggested by Peter Johns (in litt.).

Remarks: I can only distinguish A. bashfordi n. sp. and A. johnsi n. sp. by examining the gonopods of mature males. Females from the type locality for A. johnsi n. sp. are tentatively assigned to that species, as the nearest locality for A. bashfordi n. sp. is more than 50 km distant. Tentative assignment of females to A. bashfordi n. sp. is not yet possible, as much of the known range of this species is overlapped by that of A. johnsi n. sp. ( Fig. 16 ).

The surface­dwelling A. bashfordi n. sp. and A. johnsi n. sp. are superficially similar to the three most common species in the Tasmanian genus Bromodesmus ( Mesibov 2004a) : B. catrionae , B. militaris and B. rufus . All are medium­sized burrowing dalodesmids with greatly reduced paranota, well­calcified cuticle and a strongly smelling defensive secretion. Interestingly, they have not yet been found to co­occur in Tasmania ( Fig. 17 ), although the two closest known localities ( A. johnsi n. sp. and B. rufus Mesibov, 2004 in central Tasmania) are only 14 km apart.

A. clarkei n. sp. and A. eberhardi n. sp. have only been found in caves in Ordovician limestone, generally close to streams. As I have not carefully searched for surface populations near the known localities, I am not yet certain that the two species are strictly troglobitic. If they are, it is remarkable that 39 of the 42 specimens examined are mature, since the collectors, Arthur Clarke and Stefan Eberhard, are experienced field zoologists who collected much smaller invertebrates in the same cave systems. It is possible that juvenile stages of these two species are widely scattered in the caves (perhaps in narrower cave passages), and that adults congregate near larger streams when mating and dispersing. This behaviour would be similar to that inferred for the surface­dwelling but cryptic A. bashfordi n. sp. and A. johnsi n. sp., which are rarely collected by direct searching but which have often been taken as wandering adults in pitfall traps. Possible anecdotal evidence for such behaviour is noted in Eberhard et al. (1991, p. 71): “They [troglobitic millipedes, locality not specified] are sometimes found as ‘colonies’ in caves (same clutch?) and their abundance is seasonally quite variable in some caves (A. Goede pers. comm.).”

Figures

FIGURE 16. Localities for Atalopharetra bashfordi n. sp. (crosses) and A. johnsi n. sp. (squares). Circles indicate known co­occurrences.

FIGURE 17. Combined localities for species of Atalopharetra n. gen. (squares) and Bromodesmus Mesibov, 2004 (triangles). Bromodesmus localities from Mesibov (2004 a).